Novel CAD gene mutations in a boy with developmental and epileptic encephalopathy 50 with dramatic response to uridine therapy: a case report and a review of the literature

BACKGROUND

Developmental and epileptic encephalopathy-50 (DEE-50) is a rare clinical condition believed to be caused by a mutation in the CAD gene and is associated with a bleak prognosis. CAD-related diseases have a wide range of clinical manifestations and other symptoms that may be easily overlooked. Like other rare diseases, the clinical manifestations and the treatment of DEE-50 necessitate further investigation.

CASE PRESENTATION

A 1-year-old male patient presented with developmental delay, seizures, and anaemia at 3 months of age. He further developed refractory status epilepticus (SE), rapid deterioration of cognitive and motor function, and even became comatose at 5 months of age. Whole-exome sequencing of trios (WES-trios) revealed a compound heterozygous variant in the CAD gene, with one locus inherited from his father (c.1252C>T: p.Q418* nonsense mutation) and one from his mother (c.6628G>A: p.G2210S, missense mutation). This compound heterozygous CAD variant was unreported in the Human Gene Mutation Database. After uridine treatment, his cognitive faculties dramatically improved and he remained seizure-free. Forty two cases with CAD gene mutation reported in the literatures were reviewed. Among them, 90% had onset before 3 years of age, with average of 1.6±1.8 years old. The average age of diagnosis was 7.7 ± 10 years. The mortality rate was approximately 9.5%, with all reported deaths occurring in patients without uridine treatment. The clinical entity could be improved dramatically when the patient treated with uridine.

CONCLUSIONS

We present a boy with DEE 50 caused by novel CAD gene mutations and reviewed the clinical features of 42 patients reported previously. DEE 50 has early onset, refractory seizures, even status epilepticus leading to death, with favorable response to treatment with oral uridine. Early uridine treatment is recommended if CAD defect is suspected or genetically diagnosed. This study enhances the knowledge of DEE 50 and expands the spectrum of CAD gene mutations.

Selection and Characterization of DNA Aptamers for Cytidine and Uridine

Cytidine and uridine are two essential pyrimidine ribonucleotides, and accurate detection of these nucleosides holds significant biological importance. While many aptamers were reported to bind purines, little success was achieved for pyrimidine binding. This study employs the library-immobilization capture-SELEX technique to isolate aptamers capable of selectively binding to cytidine and uridine. First, a selection was performed using a mixture of cytidine and uridine as the target. This selection led to the isolation of a highly selective aptamer for cytidine with a dissociation constant (Kd ) of 0.9 μM as determined by isothermal titration calorimetry (ITC). In addition, a dual-recognition aptamer was also discovered, which exhibited selective binding to both cytidine and uridine. Subsequently, a separate selection was carried out using uridine as the sole target, and the resulting uridine aptamer displayed a Kd of 4 μM based on a thioflavin T fluorescence assay and a Kd of 102 μM based on ITC. These aptamers do not have a strict requirement of metal ions for binding, and they showed excellent selectivity since no binding was observed with their nucleobases or nucleotides. This study has resulted three aptamers for pyrimidines, which can be employed in biosensors and DNA switches.

Brequinar inhibits African swine fever virus replication in vitro by activating ferroptosis

BACKGROUND

African swine fever virus (ASFV) is one of the most fatal swine etiological agents and has a huge economic impact on the global pork industry. Given that no effective vaccines or anti-ASFV drugs are available, there remains a pressing need for novel anti-ASFV drugs. This study aimed to investigate the anti-African swine fever virus (ASFV) activity of brequinar, a DHODH inhibitor.

METHODS

The anti-ASFV activity of brequinar was investigated using IFA, HAD, HAD50, qRT-PCR, and western blotting assays. The western blotting assay was used to investigate whether brequinar inhibits ASFV replication by killing ASFV particles directly or by acting on cell factors. The confocal microscopy and western blotting assays were used to investigate whether brequinar inhibits ASFV replication by activating ferroptosis.

RESULTS

In this study, brequinar was found to effectively inhibit ASFV replication ex vivo in porcine alveolar macrophages (PAMs) in a dose-dependent manner. In kinetic studies, brequinar was found to maintain ASFV inhibition from 24 to 72 hpi. Mechanistically, the time-of-addition assay showed that brequinar exerted anti-ASFV activity in all treatment modes, including pre-, co-, and post-treatment rather than directly killing ASFV particles. Notably, FerroOrange, Mito-FerroGreen, and Liperfluo staining experiments showed that brequinar increased the accumulation of intracellular iron, mitochondrial iron, and lipid peroxides, respectively. Furthermore, we also found that ferroptosis agonist cisplatin treatment inhibited ASFV replication in a dose-dependent manner and the inhibitory effect of brequinar on ASFV was partially reversed by the ferroptosis inhibitor ferrostatin-1, suggesting that brequinar activates ferroptosis to inhibit ASFV replication. Interestingly, exogenous uridine supplementation attenuated the anti-ASFV activity of brequinar, indicating that brequinar inhibits ASFV replication by inhibiting DHODH activity and the depletion of intracellular pyrimidine pools; however, the induction of ferroptosis by brequinar treatment was not reversed by exogenous uridine supplementation, suggesting that brequinar activation of ferroptosis is not related to the metabolic function of pyrimidines.

CONCLUSIONS

Our data confirm that brequinar displays potent antiviral activity against ASFV in vitro and reveal the mechanism by which brequinar inhibits ASFV replication by activating ferroptosis, independent of inhibiting pyrimidine synthesis, providing novel targets for the development of anti-ASFV drugs.

Uridine alleviates high-carbohydrate diet-induced metabolic syndromes by activating sirt1/AMPK signaling pathway and promoting glycogen synthesis in Nile tilapia (Oreochromis niloticus)

Carbohydrates have a protein sparing effect, but long-term feeding of a high-carbohydrate diet (HCD) leads to metabolic disorders due to the limited utilization efficiency of carbohydrates in fish. How to mitigate the negative effects induced by HCD is crucial for the rapid development of aquaculture. Uridine is a pyrimidine nucleoside that plays a vital role in regulating lipid and glucose metabolism, but whether uridine can alleviate metabolic syndromes induced by HCD remains unknown. In this study, a total of 480 Nile tilapia (Oreochromis niloticus) (average initial weight 5.02 ± 0.03 g) were fed with 4 diets, including a control diet (CON), HCD, HCD + 500 mg/kg uridine (HCUL) and HCD + 5,000 mg/kg uridine (HCUH), for 8 weeks. The results showed that addition of uridine decreased hepatic lipid, serum glucose, triglyceride and cholesterol (P < 0.05). Further analysis indicated that higher concentration of uridine activated the sirtuin1 (sirt1)/adenosine 5-monophosphate-activated protein kinase (AMPK) signaling pathway to increase lipid catabolism and glycolysis while decreasing lipogenesis (P < 0.05). Besides, uridine increased the activity of glycogen synthesis-related enzymes (P < 0.05). This study suggested that uridine could alleviate HCD-induced metabolic syndrome by activating the sirt1/AMPK signaling pathway and promoting glycogen synthesis. This finding reveals the function of uridine in fish metabolism and facilitates the development of new additives in aquatic feeds.

Effects of uridine administration on hippocampal matrix metalloproteinases and their endogenous inhibitors in REM sleep-deprived rats

Rapid eye movement (REM) sleep is associated with synaptic plasticity which is considered essential for long-term potentiation (LTP). The composition of extracellular matrix (ECM), in part, plays a role in REM sleep-associated synaptic functioning. The objective of this study was to investigate the effects of uridine administration on levels of matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs) in rats subjected to REM sleep deprivation (REMSD). REMSD was induced by modified multiple platform method for 96-hour. Rats were randomized to receive either saline or uridine (1 mmol/kg) intraperitoneally twice a day for four days. Rats were then decapitated and their hippocampi were dissected for analyzing the levels of MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2 and TIMP-3 by Western-blotting and the activities of MMP-2 and MMP-9 by Gelatin zymography. REMSD resulted in reduced levels of MMP-3, MMP-9, TIMP-3 and activity of MMP-9 in saline-treated rats, while uridine treatment significantly enhanced their impairment. TIMP-1 was enhanced following REMSD but uridine treatment had no significant effect on TIMP-1 levels. MMP-2, TIMP-2 levels and MMP-2 activity were not affected by either REMSD or uridine administration. These data show that REMSD significantly affects ECM composition which is ameliorated by uridine administration suggesting a possible use of uridine in sleep disorders.

Identification of Major Antioxidant Compounds from the Edible Mushroom Basidiomycetes-X (Echigoshirayukidake)

Basidiomycetes-X, of which Japanese vernacular name is Echigoshirayukidake, is a local speciality mushroom found and cultivated in Japan that has been distributed as a precious cuisine material or as a functional food with medicinal properties. Antioxidant activity-guided isolation of major ingredients in Basidiomycetes-X revealed the presence of ergosterol, trans-10,cis-12-octadecadienoic acid (a conjugated linolenic acid, 10(E),12(Z)-CLA) and 2,3-dihydro-3,5-dihydroxy-6-methyl‑4H‑pyran-4-one (DDMP). Approximately 21% of the 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazino radical (DPPH) scavenging activities in the methanolic extract were related to 10(E),12(Z)-CLA, while approximately 6.2% of the activity was related to ergosterol. DDMP was present in both methanolic and water extracts, and the activity related to DDMP was conspicuously detected in water extracts. Moreover, uridine and adenosine were identified as major components of Basidiomycetes-X. The ingredients identified in Basidiomycetes-X are expected to be involved in biological functions observed in this mushroom, which is an attractive functional food resource.

Intestinal aging is alleviated by uridine via regulating inflammation and oxidative stress in vivo and in vitro

Many countries in the world are stepping into the aging society with the challenge of the increasing agin gpopulation. The physiological functions of the human body begins to decline with aging, and the intestinal tract as the most important digestive organ will also be aging. How to relieve or reverse aging is an important scientific problem.The aging model in vivo and in vitro was established. Western-blot, indirect immunofluorescence and immunohistochemistry were carried out to explore the anti-aging effect of uridine.In the current study, we examined the anti-aging effect of uridine in vivo and in vitro experiments. In vitro cell model, we found that the aging level of intestinal tract was significantly reduced by uridine, uridine treatment down-regulated the Sa-β-gal-positive cells. Furthermore, the levels of inflammation and oxidative stress were also significantly reduced by uridine treatment. On this basis, in vivo experiments, we found that the aging level of mice fed with uridine was significantly lower than that of the control group as demonstrated by immunohistochemistry and Western blot analyses.In conclusion, our current research indicates that uridine shows a good anti-aging effect,which suggests that uridine is expected to be used as a health food or clinical drug to treat intestinal aging.

Uridine relieves MSCs and chondrocyte senescence in vitvo and exhibits the potential to treat osteoarthritis in vivo

Osteoarthritis (OA) is a degenerative disease of extremely high incidence in the elderly. Therefore, anti-aging may be an important prerequisite for treating OA. The senescence of chondrocytes and mesenchymal stem cells (MSCs) is one of the important factors that causes OA. Here, the effect of uridine (which is a functional food derived from plants or animals) on senescence of chondrocytes and MSCs was evaluated in in vivo and in vitro experiments. For this, we established the senescence model of chondrocyte and MSCs in vitro, and established the OA model in vivo, and a series of experiments (such as CLSM, ELISA, Western blot, etc.) were conducted to evaluate the effect of uridine on chondrocyte and MSCs senescence. The results showed that uridine could alleviate chondrocyte and MSCs senescence in vitro by evaluating a series of aging markers. Furthermore, uridine could also relieve OA in vivo. In summary, in the present work, we found that uridine can alleviate chondrocyte and MSCs senescence in in vitro and in vivo experiments. Uridine has shown great potential in the treatment of OA in vivo, suggesting that uridine could be used to treat and prevent OA induced by aging, and has potential clinical applications in future.

Development of an eco-friendly and fast HPLC method for quantitative analysis of four nucleosides in Cordyceps and related products

An eco-friendly and fast HPLC method was developed for the determination of adenosine, inosine, guanosine and uridine in Cordyceps and related products (fermented mycelia of Hirsutella sinensis andPaecilomyces hepiali). The sample was ultrasonically extracted using 0.5% phosphoric acid solutions for 2.5 min. Sample separation was performed on a Poroshell SB-Aq column (50 mm × 4.6 mm, 2.7 μm) using eco-friendly mobile phase consisting of formic acid and ammonium formate aqueous solution at a flow rate of 1.0 mL·min^-1. The detection wavelength was 260 nm. The developed HPLC method showed good linearity with correlation coefficients of 1.0000 in the test range. Good precision, repeatability and stability of this method were also observed (RSD ≤ 2.81%). The recovery ranged from 91.84%-105.19% (RSD ≤ 2.59%). Compared with reported methods, the current method did not use harmful organic solvent and took only 10.5 min. It obtained a high eco-score of 91 by the "Analytical Eco-Scale" tool. The developed method is eco-friendly and fast, which is suitable for the quality evaluation of Cordyceps and related products.

A New Perspective on the Maillard Reaction and the Origin of Life

The Maillard reaction, a spontaneous 'one pot' reaction between amino acids and reducing sugars that occurs at low reactant concentrations and low temperatures, is a good candidate for having played a role in the origin of life on the Earth. In view of the probability that RNA and DNA were preceded by an evolutionary forerunner with a more straightforward prebiotic synthesis, it is a testament to the prescience of Oró and colleagues that, in 1975, they drew attention to the Maillard reaction, in particular evidence that melanoidin polymers (the end-product of the reaction) contain '…heterocyclic nitrogen compounds similar to the nitrogenous bases' (Nissenbaum in J Mol Evol 6:253-270, 1975). Indeed, reports of the Maillard reaction product, 2-Acetyl-6-(Hydroxymethyl)-5,6-Dihydro-4H-Pyridinone (AHDP), with a structure reminiscent of the pyrimidine nucleobase uracil, suggest the Maillard reaction might have played a key role in the synthesis of components of a proto-RNA polymer, with AHDP and two structurally related products predicted to be similar to uracil in the latter's ability to form non-standard base pair interactions. It is possible that the primary function of these interactions was to allow molecules such as AHDP to separate out of the prebiotic chemical clutter. If this were the case, catalysis, and coding-made possible by the polymerization of proto-nucleoside monomers into linear sequence strings-would have been evolving properties.

Guanosine and uridine alleviate airway inflammation via inhibition of the MAPK and NF-κB signals in OVA-induced asthmatic mice

Asthma is one of the most common respiratory diseases. Lack of response or poor adherence to corticosteroids demands the development of new drug candidates for asthma. Endogenous nucleosides could be potential options since uridine has been reported to have an anti-inflammatory effect in asthma model. However, its molecular pathways and whether other nucleosides have similar therapeutic effects remain untouched. Thus, we herein report our investigation into the anti-inflammatory effects of guanosine and uridine, and the related inner signaling pathways in asthma model. Present study shows that administration of guanosine or uridine can reduce lung inflammation in OVA-challenged mice. Total cell counts in BALF, cytokines such as IL-4, IL-6, IL-13, OVA-specific IgE and mRNA level of Cxcl1, Cxlc3, IL-17 and Muc5ac were decreased in asthmatic mice after treatment. Besides, the production of IL-6 in LPS/IFN-γ induced THP-1 cells was also decreased by both nucleosides. In vivo and in vitro expressions of key molecules in the MAPK and NF-κB pathways were reduced after the treatment of both compounds. These findings suggest that guanosine has a similar potential therapeutic value in asthma as uridine and they exert anti-inflammatory effects through suppression of the MAPK and NF-κB pathways.

Potential Neuroregenerative and Neuroprotective Effects of Uridine/Choline-Enriched Multinutrient Dietary Intervention for Mild Cognitive Impairment: A Narrative Review

In mild cognitive impairment (MCI) due to Alzheimer disease (AD), also known as prodromal AD, there is evidence for a pathologic shortage of uridine, choline, and docosahexaenoic acid [DHA]), which are key nutrients needed by the brain. Preclinical and clinical evidence shows the importance of nutrient bioavailability to support the development and maintenance of brain structure and function in MCI and AD. Availability of key nutrients is limited in MCI, creating a distinct nutritional need for uridine, choline, and DHA. Evidence suggests that metabolic derangements associated with ageing and disease-related pathology can affect the body's ability to generate and utilize nutrients. This is reflected in lower levels of nutrients measured in the plasma and brains of individuals with MCI and AD dementia, and progressive loss of cognitive performance. The uridine shortage cannot be corrected by normal diet, making uridine a conditionally essential nutrient in affected individuals. It is also challenging to correct the choline shortfall through diet alone, because brain uptake from the plasma significantly decreases with ageing. There is no strong evidence to support the use of single-agent supplements in the management of MCI due to AD. As uridine and choline work synergistically with DHA to increase phosphatidylcholine formation, there is a compelling rationale to combine these nutrients. A multinutrient enriched with uridine, choline, and DHA developed to support brain function has been evaluated in randomized controlled trials covering a spectrum of dementia from MCI to moderate AD. A randomized controlled trial in subjects with prodromal AD showed that multinutrient intervention slowed brain atrophy and improved some measures of cognition. Based on the available clinical evidence, nutritional intervention should be considered as a part of the approach to the management of individuals with MCI due to AD, including adherence to a healthy, balanced diet, and consideration of evidence-based multinutrient supplements.

Antioxidative effects of uridine in a neonatal rat model of hyperoxic brain injury

Background/aim

Premature birth is a major problem that results in an increased risk of mortality and morbidity. The management of such infants consists of supraphysiological oxygen therapy, which affects brain development due, in part, to the deterioration caused by reactive oxygen species (ROS). We showed previously that exogenously administered uridine provides neuroprotection in a neonatal rat model of hyperoxic brain injury. Hence, the aim of the present study was to investigate the effects of uridine on ROS in the same setting.

Materials and methods

Hyperoxic brain injury was induced by subjecting a total of 53 six-day-old rat pups to 80% oxygen (the hyperoxia group) for a period of 48 h. The pups in the normoxia group continued breathing room air (21% oxygen). Normoxia + saline or hyperoxia + saline or hyperoxia + uridine 100 mg/kg or hyperoxia + uridine 300 mg/kg or hyperoxia + uridine 500 mg/kg was injected intraperitoneally (i. p.) 15 min prior to the hyperoxia procedure. The pups were decapitated and the brains were homogenized to analyze superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), myeloperoxidase (MPO), and malondialdehyde (MDA) enzymes as well as DJ-1 (protein deglycase DJ-1) — an oxidative stress-sensitive protein.

Results

Hyperoxia-induced may cause overproduction of oxygen radicals and the oxidant/antioxidant balance may be disturbed in the brain. Brain MPO and MDA levels were significantly increased in saline-receiving pups exposed to hyperoxia. Brain SOD and GSH-Px levels were significantly decreased in saline-receiving pups exposed to hyperoxia. Our results showed that uridine administration prevented the hyperoxia-induced decrease in SOD and GSH-Px while counteracting the hyperoxia-induced increase in MPO and MDA in a dose-dependent manner. Uridine also increased the DJ-1 levels in brains of rat pups subjected to hyperoxia.

Conclusion

These data suggest that uridine exhibits antioxidative properties which may mediate the protective effects of uridine in a neonatal rat model of hyperoxic brain injury.

Region-specific metabolic characterization of the type 1 diabetic brain in mice with and without cognitive impairment

Type 1 diabetes (T1D) has been reported to cause cognitive decline, but brain metabolic changes during this process are still far from being fully understood. Here, we found that streptozotocin (STZ)-induced T1D mice exhibited impaired learning and memory at 11 weeks after STZ treatment but not at 3 weeks. Therefore, we studied metabolic alterations in six different brain regions of T1D mice with and without cognitive decline, and attempted to identify key metabolic pathways related to diabetic cognitive dysfunction. The results demonstrate that lactate had already increased in all brain regions of T1D mice prior to cognitive decline, but a decreased TCA cycle was only observed in hippocampus, cortex and striatum of T1D mice with cognitive impairment. Reduced N-acetylaspartate and choline were found in all brain regions of T1D mice, irrespective of cognitive decline. In addition, disrupted neurotransmitter metabolism was noted to occur in T1D mice before cognitive deficit. Of note, we found that the level of uridine was significantly reduced in cerebellum, cortex, hypothalamus and midbrain of T1D mice when cognitive decline was presented. Therefore, brain region-specific metabolic alterations may comprise possible biomarkers for the early-diagnosis and monitoring of diabetic cognitive decline. Moreover, down-regulated TCA cycle and pyrimidine metabolism could be closely related to T1D-associated cognitive impairment.

Visualization of Mitochondrial RNA Granules in Cultured Cells Using 5-Bromouridine Labeling

The incorporation of nucleoside analogs is a useful tool to study the various functions of DNA and RNA. These analogs can be detected directly by fluorescence or by immunolabeling, allowing to visualize, track, or measure the nucleic acid molecules in which they have been incorporated. In this chapter, methodologies to measure human mitochondrial transcription are described. The nascent RNA that is transcribed from mitochondrial DNA (mtDNA) has been shown to assemble into large ribonucleoprotein complexes that form discrete foci. These structures were called mitochondrial RNA granules (MRGs) and can be observed in vitro by the incorporation of a 5-Bromouridine (BrU), which is subsequently visualized by fluorescent immunolabeling. Here, a combined protocol for the MRGs detection is detailed, consisting of BrU labeling and visualization of one of their bona fide protein components, Fas-activated serine-threonine kinase domain 2 (FASTKD2). Based on immunodetection, the half-life and kinetics of the MRGs under various experimental conditions can further be determined by chasing the BrU pulse with an excess of Uridine.

Quantitation of uridine and L-dihydroorotic acid in human plasma by LC-MS/MS using a surrogate matrix approach

Uridine and L-dihydroorotate (DHO) are important intermediates of de novo as well as salvage pathways for the biosynthesis of pyrimidines, which are the building blocks of nucleic acids - DNA and RNA. These metabolites are known to be significant biomarkers of pyrimidine synthesis during the development of DHODH inhibitor drugs for treatment of several cancers and immunological disorders. Here we are reporting a validated LC-MS/MS assay for the quantitation of uridine and DHO in K₂EDTA human plasma. Due to presence of endogenous uridine and DHO in the biological matrix, a surrogate matrix approach with bovine serum albumin (BSA) solution was used. Human plasma samples were spiked with stable isotope labeled internal standards, processed by protein precipitation, and analyzed using LC-MS/MS. Parallelism was successfully demonstrated between human plasma (the authentic matrix) and BSA (the surrogate matrix). The linear analytical ranges of the assay were set at 30.0-30,000 ng/mL for uridine and 3.00-3,000 ng/mL for DHO. This validated LC-MS/MS method demonstrated excellent accuracy and precision. The overall accuracy was between 91.9 % and 106 %, and the inter-assay precision (%CV) were less than 4.2 % for uridine in human plasma. The overall accuracy was between 92.8 % and 106 %, and the inter-assay precision (%CV) were less than 7.2 % for DHO in human plasma. Uridine and DHO were found to be stable in human plasma for at least 24 h at room temperature, 579 days when stored at -20 °C, 334 days when stored at -70 °C, and after five freeze/thaw cycles. The assay has been successfully applied to human plasma samples to support clinical studies. Novel Aspect: A surrogate matrix approach to quantify endogenous uridine and DHO concentrations in human plasma.

Maternal supplementation with uridine influences fatty acid and amino acid constituents of offspring in a sow-piglet model

To investigate the cumulative effects of maternal supplementation with nucleotides in the form of uridine (UR) on fatty acid and amino acid constituents of neonatal piglets, fifty-two sows in late gestation were assigned randomly into the control (CON) group (fed a basal diet) or UR group (fed a basal diet with 150 g/t UR). Samples of neonates were collected during farrowing. Results showed that supplementing with UR in sows' diet significantly decreased the birth mortality of pigs (P = 0·05), and increased serum total cholesterol, HDL and LDL of neonatal piglets (P < 0·05). Moreover, the amino acid profile of serum and liver of neonatal piglets was affected by the addition of UR in sows' diets (P < 0·05). Furthermore, an up-regulation of mRNA expression of energy metabolism-related genes, including fatty acid elongase 5, fatty acid desaturase 1, hormone-sensitive lipase and cholesterol-7a-hydroxylase, was observed in the liver of neonates from the UR group. Additionally, a decrease in placental gene expression of excitatory amino acid transporters 2, excitatory amino acid transporter 3 and neutral AA transporter 1 in the UR group was concurrently observed (P < 0·05), and higher protein expression of phosphorylated protein kinase B, raptor, PPARα and PPARγ in placenta from the UR group was also observed (P < 0·05). Together, these results showed that maternal UR supplementation could regulate placental nutrient transport, largely in response to an alteration of mTORC1-PPAR signalling, thus regulating the nutrition metabolism of neonatal piglets and improving reproductive performance.

Uridine natural products: Challenging targets and inspiration for novel small molecule inhibitors

Nucleoside derivatives, in particular those featuring uridine, are familiar components of the nucleoside family of bioactive natural products. The structural complexity and biological activities of these compounds have inspired research from organic chemistry and chemical biology communities seeking to develop novel approaches to assemble the challenging molecular targets, to gain inspiration for enzyme inhibitor development and to fuel antibiotic discovery efforts. This review will present recent case studies describing the total synthesis and biosynthesis of uridine natural products, and de novo synthetic efforts exploiting features of the natural products to produce simplified scaffolds. This research has culminated in the development of complementary strategies that can lead to effective uridine-based inhibitors and antibiotics. The strengths and challenges of the juxtaposing methods will be illustrated by examining select uridine natural products. Moreover, structure-activity relationships (SAR) for each natural product-inspired scaffold will be discussed, highlighting the impact on inhibitor development, with the aim of future uridine-based small molecule expansion.

Assessment of glutamatergic synaptic transmission and plasticity in brain slices: relevance to bioelectronic approaches

Background

Glutamatergic neurons represent the largest neuronal class in the brain and are responsible for the bulk of excitatory synaptic transmission and plasticity. Abnormalities in glutamatergic neurons are linked to several brain disorders and their modulation represents a potential opportunity for emerging bioelectronic medicine (BEM) approaches. Here, we have used a set of electrophysiological assays to identify the effect of the pyrimidine nucleoside uridine on glutamatergic systems in ex vivo brain slices. An improved understanding of glutamatergic synaptic transmission and plasticity, through this type of examination, is critical to the development of potential neuromodulation strategies.

Methods

Ex vivo hippocampal slices (400 μm thick) were prepared from mouse brain. We recorded field excitatory postsynaptic potentials (fEPSP) in the CA1’s stratum radiatum by stimulation of the CA3 Schaeffer collateral/commissural axons. Uridine was applied at concentrations (3, 30, 300 μM) representing the physiological range present in brain tissue. Synaptic function was studied with input-output (I-O) functions, as well as paired-pulse facilitation (PPF). Synaptic plasticity was studied by applying tetanic stimulation to induce post-tetanic potentiation (PTP), short-term potentiation (STP) and long-term potentiation (LTP). Additionally, we determined whether uridine affected synaptic responses carried solely by n-methyl-d-aspartate receptors (NMDARs), particularly during the oxygen-glucose deprivation (OGD) paradigm.

Results

The presence of uridine altered glutamatergic synaptic transmission and plasticity. We found that uridine affected STP and LTP in a concentration-dependent manner. Low-dose uridine (3 μM) had no effect, but higher doses (30 and 300 μM) impaired STP and LTP. Moreover, uridine (300 μM) decreased NMDAR-mediated synaptic responses. Conversely, uridine (at all concentrations tested) had a negligible effect on PPF and basal synaptic transmission, which is mediated primarily by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). In addition, uridine (100 μM) exerted a protective effect when the hippocampal slices were challenged with OGD, a widely used model of cerebral ischemia.

Conclusions

Using a wide set of electrophysiological assays, we identify that uridine interacts with glutamatergic neurons to alter NMDAR-mediated responses, impair synaptic STP and LTP in a dose-dependent manner, and has a protective effect against OGD insult. This work outlines a strategy to identify deficits in glutamatergic mechanisms for signaling and plasticity that may be critical for targeting these same systems with BEM device-based approaches. To improve the efficacy of potential neuromodulation approaches for treating brain dysfunction, we need to improve our understanding of glutamatergic systems in the brain, including the effects of modulators such as uridine.

Improve uridine production by modifying related metabolic pathways in Bacillus subtilis

OBJECTIVES

The metabolic pathway related to uridine production was modified in Bacillus subtilis in order to increase the production of uridine.

RESULTS

Decreasing the relative transcriptional level of pur operon in Bacillus subtilis TD300 to 80%, and the production of the derived strain TD312 was increased to 11.81 g uridine/l and the yield was increased to 270 mg uridine/g glucose. The expression of pucR gene in situ by P_ccpA resulting in a 194.01-fold increase in the relative transcriptional level of pucR gene and 349.71-fold increase in the relative transcriptional level of ure operon, respectively. Furthermore, the production of TD314 reached 13.06 g uridine/l, while the yield reached 250 mg uridine/g glucose.

CONCLUSION

This is the first report that more than 13 g uridine/l with a yield of 250 mg uridine/g glucose is produced in shake flask fermentation of genetically engineered Bacillus subtilis.

iPseU-NCP: Identifying RNA pseudouridine sites using random forest and NCP-encoded features

Background

Pseudouridine modification is most commonly found among various kinds of RNA modification occurred in both prokaryotes and eukaryotes. This biochemical event has been proved to occur in multiple types of RNAs, including rRNA, mRNA, tRNA, and nuclear/nucleolar RNA. Hence, gaining a holistic understanding of pseudouridine modification can contribute to the development of drug discovery and gene therapies. Although some laboratory techniques have come up with moderately good outcomes in pseudouridine identification, they are costly and required skilled work experience. We propose iPseU-NCP – an efficient computational framework to predict pseudouridine sites using the Random Forest (RF) algorithm combined with nucleotide chemical properties (NCP) generated from RNA sequences. The benchmark dataset collected from Chen et al. (2016) was used to develop iPseU-NCP and fairly compare its performances with other methods.

Results

Under the same experimental settings, comparing with three state-of-the-art methods including iPseU-CNN, PseUI, and iRNA-PseU, the Matthew’s correlation coefficient (MCC) of our model increased by about 20.0%, 55.0%, and 109.0% when tested on the H. sapiens (H_200) dataset and by about 6.5%, 35.0%, and 150.0% when tested on the S. cerevisiae (S_200) dataset, respectively. This significant growth in MCC is very important since it ensures the stability and performance of our model. With those two independent test datasets, our model also presented higher accuracy with a success rate boosted by 7.0%, 13.0%, and 20.0% and 2.0%, 9.5%, and 25.0% when compared to iPseU-CNN, PseUI, and iRNA-PseU, respectively. For majority of other evaluation metrics, iPseU-NCP demonstrated superior performance as well.

Conclusions

iPseU-NCP combining the RF and NPC-encoded features showed better performances than other existing state-of-the-art methods in the identification of pseudouridine sites. This also shows an optimistic view in addressing biological issues related to human diseases.

Use of nucleoside phosphorylases for the preparation of 5-modified pyrimidine ribonucleosides

Enzymatic transglycosylation, a transfer of the carbohydrate moiety from one heterocyclic base to another, is catalyzed by nucleoside phosphorylases (NPs) and is being actively developed and applied for the synthesis of biologically important nucleosides. Here, we report an efficient one-step synthesis of 5-substitited pyrimidine ribonucleosides starting from 7-methylguanosine hydroiodide in the presence of nucleoside phosphorylases (NPs).

Short-Term Oral UMP/UR Administration Regulates Lipid Metabolism in Early-Weaned Piglets

Simple Summary

Uridine monophosphate (UMP) and uridine (UR) are rich in sow’s milk. The results from this study showed that UMP and UR affect the lipid profile and lipid metabolism in weanling piglets. It is suggested that UMP and UR improve the energy status in early-weaned piglets.

Abstract

As a main ingredient of milk, the nucleotides content is about 12–58 mg/g, which plays a critical role in maintaining cellular function and lipid metabolism. This study was conducted to evaluate the effects of short-term uridine monophosphate (UMP) and uridine (UR) administration on lipid metabolism in early-weaned piglets. Twenty-one weaned piglets (7 d of age; 3.32 ± 0.20 kg average body weight) were randomly assigned into three groups: The control (CON), UMP, and UR group, and oral administered UMP or UR for 10 days, respectively. The results showed that supplementation with UMP significantly increased (p < 0.05) serum low density lipoprotein (LDL) and tended to increase (p = 0.062) serum total cholesterol (TC) content of piglets when compared with the other two groups. Oral administration with UMP and UR significantly decreased (p < 0.05) the serum total bile acid (TBA) and plasma free fatty acids (FFA) of piglets, and significantly reduced the fatty acid content of C12:0 (p < 0.01) and C14:0 (p < 0.05) in liver. Experiments about key enzymes that are involved in de novo synthesis of fatty acid showed that the gene expression of liver X receptors (LXRα), sterol regulatory element-binding transcription factor 1 (SREBP1c), fatty acid desaturase 2 (FADS2), and fatty acid elongase 5 (ELOVL5) were remarkably down-regulated (p < 0.05) with UMP and UR treatment, and key factors of adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), and carnitine palmitoyl transferase 1 (CPT-1α) involved in fatty acid catabolism were also decreased (p < 0.05). Additionally, the protein expression of phosphorylated-mTOR was not affected while phosphorylation of AKT was repressed (p < 0.05). In conclusion, short-term oral UMP or UR administration could regulate fatty acid composition and lipid metabolism, thus providing energy for early-weaned piglets.

Discovery of small molecule inhibitors of human uridine-cytidine kinase 2 by high-throughput screening

Clinically relevant inhibitors of dihydroorotate dehydrogenase (DHODH), a rate-limiting enzyme in mammalian de novo pyrimidine synthesis, have strong antiviral and anticancer activity in vitro. However, they are ineffective in vivo due to efficient uridine salvage by infected or rapidly dividing cells. The pyrimidine salvage enzyme uridine-cytidine kinase 2 (UCK2), a ∼29 kDa protein that forms a tetramer in its active state, is necessary for uridine salvage. Notwithstanding the pharmacological potential of this target, no medicinally tractable inhibitors of the human enzyme have been reported to date. We therefore established and miniaturized an in vitro assay for UCK2 activity and undertook a high-throughput screen against a ∼40,000-compound library to generate drug-like leads. The structures, activities, and modes of inhibition of the most promising hits are described. Notably, our screen yielded non-competitive UCK2 inhibitors which were able to suppress nucleoside salvage in cells both in the presence and absence of DHODH inhibitors.

Development and validation of an HPLC-DAD-MS method for determination of four nucleoside compounds in the New Zealand native mushroom Hericium sp

To identify and quantify the content of nucleoside compounds in the New Zealand native edible mushroom Hericium sp., a high-performance liquid chromatography coupled with a triple quadrupole detector mass method was developed and validated. Four nucleoside substitutes, namely cytidine, uridine, adenosine, and guanosine, were identified. Optimization was conducted to study the effect of extraction method type, solvent pH, and extraction time. The optimal conditions were obtained using ultrasonic treatment in water at pH 3.8 for 30 min. For chromatographic separation, a C₁₈ column was applied using 0.1% formic acid (pH 3.4) as the mobile phase with detection at 260 nm. The total concentration of the four nucleoside compounds was high, at 10.7 mg/g dry weight, indicating a potential benefit for human health. The excellent validation results based on selectivity, linearity, precision, accuracy and robustness revealed the reliability of the newly developed analytical method, which could be applied routinely in research laboratories.

Modified Quadrupole Ion Trap Mass Spectrometer for Infrared Ion Spectroscopy: Application to Protonated Thiated Uridines

Modifications to a Paul-type quadrupole ion trap mass spectrometer providing optical access to the trapped ion cloud as well as hardware and software for coupling to a table-top IR optical parametric oscillator laser (OPO) are detailed. Critical experimental parameters for infrared multiple photon dissociation (IRMPD) on this instrument are characterized. IRMPD action spectra, collected in the hydrogen-stretching region with this instrument, complemented by spectra in the IR fingerprint region acquired at the FELIX facility, are employed to characterize the structures of the protonated forms of 2-thiouridine, [s²Urd+H]⁺, and 4-thiouridine, [s⁴Urd+H]⁺. The measured spectra are compared with predicted linear IR spectra calculated at the B3LYP/6-311+G(d,p) level of theory to determine the conformers populated in the experiments. This comparison indicates that thiation at the 2- or 4-positions shifts the protonation preference between the 2,4-H tautomer and 4-protonation in opposite directions versus canonical uridine, which displays a roughly equal preference for the 2,4-H tautomer and O4 protonation. As found for canonical uridine, protonation leads to a mixture of conformers exhibiting C2'-endo and C3'-endo sugar puckering with an anti nucleobase orientation being populated for both 2- and 4-thiated uridine. Graphical Abstract ᅟ.

Metabolic engineering of Escherichia coli for high-yield uridine production

Uridine is a kind of pyrimidine nucleoside that has been widely applied in the pharmaceutical industry. Although microbial fermentation is a promising method for industrial production of uridine, an efficient microbial cell factory is still lacking. In this study, we constructed a metabolically engineered Escherichia coli capable of high-yield uridine production. First, we developed a CRISPR/Cas9-mediated chromosomal integration strategy to integrate large DNA into the E. coli chromosome, and a 9.7 kb DNA fragment including eight genes in the pyrimidine operon of Bacillus subtilis F126 was integrated into the yghX locus of E. coli W3110. The resultant strain produced 3.3 g/L uridine and 4.5 g/L uracil in shake flask culture for 32 h. Subsequently, five genes involved in uridine catabolism were knocked out, and the uridine titer increased to 7.8 g/L. As carbamyl phosphate, aspartate, and 5'-phosphoribosyl pyrophosphate are important precursors for uridine synthesis, we further modified several metabolism-related genes and synergistically improved the supply of these precursors, leading to a 76.9% increase in uridine production. Finally, nupC and nupG encoding nucleoside transport proteins were deleted, and the extracellular uridine accumulation increased to 14.5 g/L. After 64 h of fed-batch fermentation, the final engineered strain UR6 produced 70.3 g/L uridine with a yield and productivity of 0.259 g/g glucose and 1.1 g/L/h, respectively. To the best of our knowledge, this is the highest uridine titer and productivity ever reported for the fermentative production of uridine.

Potential role of the ecto-5'-nucleotidase in morphine-induced uridine release and neurobehavioral changes

There is growing evidence that uridine may act as an endogenous neuromodulator with a potential signaling role in the central nervous system in addition to its function in pyrimidine metabolism. We previously found that acute morphine treatment significantly increased uridine release in the dorsal striatum of mice, indicating that uridine may contribute to morphine-induced neurobehavioral changes. In the present study, we analyzed the mechanism involved in morphine-induced uridine release and the role of uridine in morphine-induced neurobehavioral changes. Uridine release in the dorsal striatum of mice was assessed by in vivo microdialysis coupled with high performance liquid chromatography (HPLC) after morphine treatment. Western blotting and immunofluorescence were used to evaluate the expression of uridine-related proteins. Morphine-induced neurobehavioral changes were assessed by locomotor activity, behavioral sensitization and conditioned place preference (CPP) test. The expression of NT5E, an extracellular enzyme involved in formation of nucleosides, including uridine, was specifically knocked down in the dorsal striatum of mice using adeno-associated virus (AAV)-mediated short hairpin RNA (shRNA). The results indicated that both acute and chronic morphine administration significantly increased uridine release in the dorsal striatum, and this was associated with upregulation of NT5E but not other uridine-related proteins. Inhibition of NT5E with APCP or shRNA markedly inhibited morphine-induced uridine release in the dorsal striatum and related neurobehavioral changes, including hyperlocomotor activity, behavioral sensitization and CPP. Our data give a better understanding of the contribution of NT5E to morphine-induced uridine release and neurobehavioral changes, and identify NT5E as a potential target for treating morphine abuse.

The role of mitochondrial KATP channel in anti-inflammatory effects of uridine in endotoxemic mice

In this study, we examined the effects of uridine on plasma cytokine levels, heat shock protein (HSP) 72 expression, and nuclear factor (NF)-κB signaling in spleen lymphocytes after exposure of male BALB/c mice to Escherichia coli lipopolysaccharide (LPS). Mice were treated with uridine (30 mg/kg body weight, intraperitoneal injection [i.p.]) or saline solution of LPS (2.5 mg/kg, i. p.). Endotoxin increased plasma levels of tumor necrosis factor-α, interferon-γ, interleukin (IL)-1, IL-2, and IL-6 by 2.1-, 1.9-, 1.7-, 1.6-, and 2.3-fold, respectively. Prior treatment with uridine prevented LPS-induced increases in all studied cytokines. In splenic lymphocytes, LPS treatment increased the expression of HSP 72 by 2.4-fold, whereas preliminary treatment with uridine completely prevented this effect. LPS also activated NF-κB signaling in splenic lymphocytes, and uridine decreased NF-κB pathway activity. Inhibitory analysis showed that the mechanism of uridine action was associated with the formation of the UDP-metabolic activator of the mitochondrial ATP-dependent potassium channel (mitoK_ATP) and the UTP-activator of glycogen synthesis in the tissues. A specific inhibitor of mitoK_ATP, 5-hydroxydecanoate (5 mg/kg), and an inhibitor of glycogen synthesis, galactosamine (110 mg/kg), prevented the effects of uridine. Thus, uridine itself or uridine phosphates, which increased after uridine treatment, appeared to inhibit pro-inflammatory responses induced by LPS application. Overall, these findings demonstrated that the mechanisms mediating the effects of uridine were regulated by activation of glycogen synthesis and opening of the mitoK_ATP, which in turn increased the energy potential of the cell and reduced oxidative stress.

Antiepileptic effect of uridine may be caused by regulating dopamine release and receptor expression in corpus striatum

Uridine is a potential endogenous neuromodulator studied for several decades for its antiepileptic effect, but the results were controversial. One remarkable feature of uridine is its regulatory action on the dopaminergic pathways. In this study, the changes in uridine and dopamine (DA) release were examined in the mouse corpus striatum after pilocarpine (PC) intraperitoneal injection. Then, the effect of uridine pre-treatment on DA release and expression of dopamine receptor (DR) was determined. The results revealed an increased uridine release initially, followed by a downward trend after an injection of 400-mg/kg PC. However, the DA release continuous increased significantly. The expression of dopamine receptor-1 (D1R) increased in a dose-dependent manner while that of dopamine receptor-2 (D2R) decreased significantly. Prophylactic administration of uridine significantly relieved the high-frequency and high-amplitude expression induced by PC as well as dose-dependently reversed the PC-induced changes in DA and DRs levels. These findings suggested that uridine produced an antiepileptic effect, which might have been mediated in part by interfering with the dopaminergic system.

5-fluorouracil Toxicity Mechanism Determination in Human Keratinocytes: in vitro Study on HaCaT Cell Line

5-fluorouracil (5-FU) and capecitabine therapy is often accompanied by palmar-plantar erythrodysesthesia (PPE) which is manifestation of 5-FU toxicity in keratinocytes. The main mechanisms of 5-FU action are thymidylate synthase (TS) inhibition which can be abrogated by thymidine and strengthened by calciumfolinate (CF) and incorporation of fluorouridinetriphosphate into RNA which can be abrogated by uridine. For proper PPE treatment 5-FU mechanism of action in keratinocytes needs to be elucidated. We used the 5-FU toxicity modulators uridine, thymidine and CF to discover the mechanism of 5-FU action in human keratinocyte cell line HaCaT. To measure the cellular viability, we used MTT test and RTCA test. CF did not augment 5-FU toxicity and 5-FU toxicity was weakened by uridine. Therefore, the primary mechanism of 5-FU toxicity in keratinocytes is 5-FU incorporation into RNA. The uridine protective effect cannot fully develop in the presence of CF. Thymidine addition to 5-FU and uridine treated cells not only prevents the toxicity-augmenting CF effect but it also prolongs the 5-FU treated cells survival in comparison to uridine only. Therefore, it can be assumed that in the presence of uridine the 5-FU toxicity mechanism is switched from RNA incorporation to TS inhibition. Although particular 5-FU toxicity mechanisms were previously described in various cell types, this is the first time when various combinations of pyrimidine nucleosides and CF were used for 5-FU toxicity mechanism elucidation in human keratinocytes. We suggest that for PPE treatment ointment containing uridine and thymidine should be further clinically tested.

Synthesis and interaction of sterol-uridine conjugate with DMPC liposomes studied by differential scanning calorimetry

Differential scanning calorimetry (DSC) is a thermoanalytical technique which provides information on the interaction between drugs and models of cell membranes. Studies on the calorimetric behavior of hydrated phospholipids within liposomes are employed to shed light on the changes in the physico-chemical properties when interacting with drugs. In this report, new potential anti-cancer drugs such as uridine and uridine derivatives (acetonide and its succinate), 3β-5α,8α-endoperoxide-cholestan-6-en-3-ol (5,8-epidioxicholesterol) and conjugate (uridine acetonide-epidioxicholesterol succinate) have been synthesized. Steglich esterification method using coupling agents allowed to obtain the uridine acetonide-sterol conjugate. The study on the interaction between the drugs and dimiristoyl-phophatidilcholine (DMPC) liposomes has been conducted by the use of DSC. The analysis of the DSC curves indicated that the uridine and derivatives (acetonide and its succinate) present a very soft interaction with the DMPC liposomes, whereas the 5,8-epidioxicholesterol and the conjugate showed a strong effect on the thermotropic behavior. Our results suggested that the lipophilic character of uridine acetonide-sterol conjugate improves the affinity with the DMPC liposomes.

Adipocyte Xbp1s overexpression drives uridine production and reduces obesity

Objective

The spliced transcription factor Xbp1 (Xbp1s), a transducer of the unfolded protein response (UPR), regulates lipolysis. Lipolysis is stimulated by fasting when uridine synthesis is also activated in adipocytes.

Methods

Here we have examined the regulatory role Xbp1s in stimulation of uridine biosynthesis in adipocytes and triglyceride mobilization using inducible mouse models.

Results

Xbp1s is a key molecule involved in adipocyte uridine biosynthesis and release by activation of carbamoyl-phosphate synthetase 2, aspartate transcarbamylase, dihydroorotase (CAD), the rate-limiting enzyme for UMP biosynthesis. Adipocyte Xbp1s overexpression drives energy mobilization and protects mice from obesity through activation of the pyrimidine biosynthesis pathway.

Conclusion

These observations reveal that Xbp1s is a potent stimulator of uridine production in adipocytes, enhancing lipolysis and invoking a potential anti-obesity strategy through the induction of a futile biosynthetic cycle.

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ER stress is a key mechanism of obesity-related metabolic disorders.

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Xbp1s, a key transducer of ER stress response, stimulates uridine biosynthesis.

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Uridine synthesized in adipocytes is critical for plasma uridine supply.

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Stimulation of uridine synthesis in adipocyte by Xbp1s promotes weight loss.

Correlation between laxative effects of uridine and suppression of ER stress in loperamide induced constipated SD rats

A correlation between endoplasmic reticulum (ER) stress and laxative effects was first reported in a constipation model treated with an aqueous extract of Liriope platyphylla (AEtLP) roots. To investigate the correlation between the laxative effect of uridine (Urd) and ER stress response, alterations in the key parameters for ER stress were measured in loperamide (Lop) induced constipation Sprague Dawley (SD) rats treated with Urd. The efficacy of the laxative effect of Urd was notable on the symptoms of chronic constipation, including alteration of stool parameters and structure of the transverse colon, in Lop induced constipated SD rats. In the PERK/eIF2-ATF4 pathway of ER stress response, the levels of eukaryotic initiation factor 2 alpha (eIF2α) phosphorylation and DNA damage-inducible protein (GADD34) transcripts were significantly enhanced in the Lop+Vehicle treated group. However, the levels were restored in the Lop+Urd treated group, although few differences were detected in the decrease rate. Similar changes were observed for levels of inositol-requiring enzyme 1 beta (IRE1β) phosphorylation and X-box binding protein 1 (XBP-1) transcript in the IRE1α/XBP pathway. Furthermore, the number of ER stress-induced apoptotic cells and Bax and Bcl-2 expression were recovered in the Lop+Urd treated group compared to the Lop+Vehicle treated group. The results of the present study therefore provide first evidence that the laxative effects of Urd may be tightly correlated with the recovery of ER stress response in constipation models.

Uridine attenuates morphine-induced conditioned place preference and regulates glutamate/GABA levels in mPFC of mice

Several lines of evidence suggest that uridine, as a neuromodulator, plays an important role in drug addiction. We previously found that uridine circumvents morphine-induced behavioral sensitization by decreasing the extracellular dopamine levels in the dorsal striatum. In the present study, the effects of uridine on morphine-induced conditioned place preference (CPP) and the possible roles of glutamate and GABA in the stress-induced reinstatement of CPP were investigated. First, the effects of uridine (1, 10 and 100mg/kg, i.p.) on the four defined phases - acquisition, expression, extinction and reinstatement (drug priming and restraint stress) - of morphine-induced CPP were studied. The results showed that pretreatment with uridine significantly blocked the acquisition and expression phases of CPP. Additionally, uridine also facilitated CPP extinction and inhibited stress-induced CPP reinstatement, although it failed to affect drug-induced CPP reinstatement. Since glutamatergic and GABAergic systems are both involved in CPP reinstatement, the extracellular levels of glutamate and GABA in the mPFC during the stress-induced CPP reinstatement were determined using in vivo microdialysis. The results showed that uridine attenuated the stress-induced glutamate increase in the mPFC without influencing the basal glutamate levels, and increased the levels of extracellular GABA in the mPFC both under normal physiological conditions and after the stress stimulus. Thus, our results indicate that uridine depresses the stress-induced reinstatement of CPP, simultaneously regulating glutamatergic and GABAergic neurotransmission in the mPFC. The present work provides further understanding of the role of uridine in morphine-induced neurobehavioral changes.

Monophosphorylation by deoxycytidine kinase affects apparent cellular uptake of decitabine in HCT116 colon cancer cells

Decitabine (DAC), a nucleoside-related DNA methylation inhibitor, is taken up into cancer cells via equilibrative nucleoside transporter 1 (ENT1), and is then monophosphorylated by deoxycytidine kinase (dCK). In the present study, we examined the contribution of dCK to the uptake of DAC in HCT116 colon cancer cells. Irinotecan and etoposide inhibited the uptake of [³H]-uridine and [³H]-DAC at 10 s and 5 min, while cytarabine and gemcitabine only inhibited that of [³H]-DAC at 5 min. Irinotecan and etoposide inhibited [³H]-DAC uptake in negative control small interfering RNA (siRNA)- or dCK siRNA-transfected cells at 10 s, whereas cytarabine and gemcitabine did not. Cytarabine and gemcitabine inhibited DAC monophosphate generation by the cytosolic proteins of HCT116 cells and recombinant human dCK protein, assessed using polyethylenimine cellulose thin-layered chromatography. Simulations using simple kinetic models showed that apparent DAC uptake in dCK and ENT1 siRNA-treated cells was attributed to its conversion to monophosphates or a decrease in the cellular flux, respectively, and that the apparent uptake of DAC in dCK-knockdown and ENT1-knockdown cells was similar at longer times, but differed at a very short time. These results suggest that the apparent uptake of DAC is affected by ENT1 and dCK in HCT116 cells.

Nutrients required for phospholipid synthesis are lower in blood and cerebrospinal fluid in mild cognitive impairment and Alzheimer's disease dementia

INTRODUCTION

Synaptic membrane formation depends on nutrients that fuel metabolic pathways for the synthesis of constituent phospholipids. Consequently, insufficient availability of such nutrients may restrict membrane formation and contribute to synaptic dysfunction in Alzheimer's disease (AD). We assessed whether blood and cerebrospinal fluid (CSF) concentrations of nutrients related to phospholipid synthesis differ among patients with AD, mild cognitive impairment (MCI), and control subjects.

METHODS

Concentrations of uridine, choline, folate, homocysteine, and other related metabolites were analyzed in paired blood and CSF samples from subjects selected from the Amsterdam Dementia Cohort with AD (n = 150; age, 66 ± 7 years; 37% female), MCI (n = 148; age, 66 ± 8 years; 37% female), and control subjects (n = 148; age, 59 ± 8 years; 38% female).

RESULTS

Age- and gender-adjusted analysis of variance revealed different concentrations of circulating uridine, choline, and folate and CSF uridine, folate, and homocysteine (all P < .05) among the three diagnostic groups. Post hoc pairwise comparison showed that subjects with AD had lower CSF uridine, plasma choline and higher CSF homocysteine concentrations, whereas subjects with MCI had lower plasma and CSF uridine, serum and CSF folate, and higher CSF homocysteine concentrations compared with control subjects (all P < .05), with differences ranging from -11 to +22%.

DISCUSSION

AD and MCI patients have lower levels of nutrients involved in phospholipid synthesis. The current observations warrant exploration of the application of nutritional strategies in the early stages of AD.

Comparison of human erythrocyte purine nucleotide metabolism and blood purine and pyrimidine degradation product concentrations before and after acute exercise in trained and sedentary subjects

This study aimed at evaluating the concentration of erythrocyte purine nucleotides (ATP, ADP, AMP, IMP) in trained and sedentary subjects before and after maximal physical exercise together with measuring the activity of purine metabolism enzymes as well as the concentration of purine (hypoxanthine, xanthine, uric acid) and pyrimidine (uridine) degradation products in blood. The study included 15 male elite rowers [mean age 24.3 ± 2.56 years; maximal oxygen uptake (VO_2max) 52.8 ± 4.54 mL/kg/min; endurance and strength training 8.2 ± 0.33 h per week for 6.4 ± 2.52 years] and 15 sedentary control subjects (mean age 23.1 ± 3.41 years; VO_2max 43.2 ± 5.20 mL/kg/min). Progressive incremental exercise testing until refusal to continue exercising was conducted on a bicycle ergometer. The concentrations of ATP, ADP, AMP, IMP and the activities of adenine phosphoribosyltransferase (APRT), hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and phosphoribosyl pyrophosphate synthetase (PRPP-S) were determined in erythrocytes. The concentrations of hypoxanthine, xanthine, uric acid and uridine were determined in the whole blood before exercise, after exercise, and 30 min after exercise testing. The study demonstrated a significantly higher concentration of ATP in the erythrocytes of trained subjects which, in part, may be explained by higher metabolic activity on the purine re-synthesis pathway (significantly higher PRPP-S, APRT and HGPRT activities). The ATP concentration, just as the ATP/ADP ratio, as well as an exercise-induced increase in this ratio, correlates with the VO_2max level in these subjects which allows them to be considered as the important factors characterising physical capacity and exercise tolerance. Maximal physical exercise in the group of trained subjects results not only in a lower post-exercise increase in the concentration of hypoxanthine, xanthine and uric acid but also in that of uridine. This indicates the possibility of performing high-intensity work with a lower loss of not only purine but also pyrimidine.

Supplementation of docosahexaenoic acid (DHA), vitamin D3 and uridine in combination with six weeks of cognitive and motor training in prepubescent children: a pilot study

Background

Learning and memory have been shown to be influenced by combination of dietary supplements and exercise in animal models, but there is little available evidence from human subjects. The aim of this pilot study was to investigate the effect of combining a motor- and cognitive exercise program with dietary supplementation consisting of 500 mg docosahexaenoic acid (DHA), 10 μg vitamin D₃ and 1000 mg uridine (DDU-supplement) in 16 prepubescent children (age 8–11 years).

Methods

We designed a randomized, placebo-controlled, double-blinded study lasting 6 weeks in which DDU-supplement or placebo was ingested daily. During the intervention period, all children trained approximately 30 min 3 days/week using an internet-based cognitive and motor training program (Mitii). Prior to and post the intervention period dietary record, blood sampling, physical exercise tests and motor and cognitive tests were performed.

Results

Fourteen of the 16 children completed the intervention and ingested the supplement as required. 6 weeks DDU-supplementation resulted in a significant increase in the blood concentration of vitamin D₂₊₃ and DHA (p = 0.023 and p < 0.001, respectively). Power calculation based on one of the cognitive tasks revealed a proper sample size of 26 children.

Conclusion

All children showed improved performance in the trained motor- and cognitive tasks, but it was not possible to demonstrate any significant effects on the cognitive tests from the dietary supplementation. However, DDU-supplementation did result in increased blood concentration of DHA and vitamin D₂₊₃.

Trial registration

Clinical registration ID: NCT02426554 (clinical Trial.gov). January 2015 retrospectively registered.

Gut-brain and brain-gut axis in Parkinson's disease models: Effects of a uridine and fish oil diet

Recent investigations have focused on the potential role of gastrointestinal (GI) abnormalities in the pathogenesis of Parkinson's disease (PD). The 'dual-hit' hypothesis of PD speculates that a putative pathogen enters the brain via two routes: the olfactory system and the GI system. Here, we investigated (1) whether local exposures of the neurotoxin rotenone in the gut or the brain of mice could induce PD-like neurological and GI phenotypes as well as a characteristic neuropathology in accordance with this 'dual-hit hypothesis' and (2) the effects of a diet containing uridine and fish oil providing docosahexaenoic acid (DHA), in both models. Mice were given rotenone either orally or by an injection in the striatum. Dietary interventions were started 1 week before rotenone exposures. We found that (1) both oral and intrastriatal administration of rotenone induced similar PD-like motor deficits, dopaminergic cell loss, delayed intestinal transit, inflammation, and alpha-synuclein accumulation in the colon; (2) the uridine and DHA containing diet prevented rotenone-induced motor and GI dysfunctions in both models. The models suggest possible bidirectional communication between the gut and the brain for the genesis of PD-like phenotype and pathology. The dietary intervention may provide benefits in the prevention of motor and non-motor symptoms in PD.

Uridine stimulate laxative effect in the loperamide-induced constipation of SD rats through regulation of the mAChRs signaling pathway and mucin secretion

Background

Uridine (Urd), which has been reported as a major component of RNA, plays an important role in various biological process including neuroprotection, biochemical modulation and glycolysis, although its role in constipation has yet to be established. Therefore, in this study, we investigated the laxative effects of Urd on chronic constipation.

Methods

The constipation phenotypes and their related mechanisms were investigated in the transverse colons of SD rats with loperamide (Lop)-induced constipation after treatment with 100 mg/kg of Urd.

Results

The number, weight and water contents of stools were significantly higher in the Lop + Urd treated group than the Lop + Vehicle treated group, while food intake and water consumption of the same group were maintained at a constant level. The thickness of the mucosa layer, muscle and flat luminal surface, as well as the number of goblet cells, paneth cells and lipid droplets were enhanced in the Lop + Urd treated group. Furthermore, the expression of the muscarinic acetylcholine receptors M2 and M3 (mAChR M2 and M3) at the transcriptional and translational level was recovered in the Lop + Urd treated group, while some markers such as Gα and inositol triphosphate (IP3) in their downstream signaling pathway were completely recovered by Urd treatment. Moreover, the ability for mucin secretion and the expression of membrane water channel (aquaporine 8, AQP8) were increased significantly in the Lop + Urd treated group compared with Lop + Vehicle treated group. Finally, the activity of Urd was confirmed in primary smooth muscle of rat intestine cells (pRISMC) based on Gα expression and IP3 concentration.

Conclusions

The results of the present study provide the first strong evidence that Urd can be considered an important candidate for improving chronic constipation induced by Lop treatment in animal models.

New N-substituted hydrazones, derivatives of uridyl aldehyde

N-substituted isomeric hydrazones of uridyl aldehyde have been synthesized. The occurrence of the dominant E isomers with respect to the azomethine group was confirmed by means of NMR spectroscopy. Synthesized hydrazones feature an acetonide moiety as a protection of two hydroxyl groups on the ribose part. The attempt to remove the protecting group resulted in an azo-hydrazone tautomeric mixture. The described compounds may be valuable chiral ligands for metal chelation. Assessment of manganese(II) ion affinity to one selected hydrazone was performed.

Botrytis cinerea can import and utilize nucleosides in salvage and catabolism and BcENT functions as high affinity nucleoside transporter

Nucleotide de novo synthesis is an essential pathway in nearly all organisms. Transport processes as well as salvage and catabolism of nucleotides and pathway intermediates are required to balance nucleotide pools. We have analysed the genome of the fungal plant pathogen Botrytis cinerea for genes involved in nucleotide metabolism and found a complete set of genes necessary for purine and pyrimidine uptake and salvage based on homology of the gene products to corresponding proteins from Aspergillus nidulans. Candidate genes required for a complete purine catabolic sequence were identified in addition. These analyses were complemented by growth tests showing functional transport and salvage activity for pyrimidines. Growth of B. cinerea mycelium in nitrogen free medium could be restored by addition of purines, indicating the presence of a functional purine catabolism, whereas pyrimidines did not support growth. Bcin07g05490 (BcENT) was identified as sole member of the equilibrative nucleoside transporter (ENT) family. The protein synthesized in Saccharomyces cerevisiae revealed high affinity transport of adenosine (KM = 6.81 μM) and uridine (KM=9.04 μM). Furthermore, a BcENT knockout mutant was generated and tested in a range of growth and infection assays. These results provide detailed insight in the use of externally supplied nucleobases and nucleosides by B. cinerea.

Benefit of uridine triacetate (Vistogard) in rescuing severe 5-fluorouracil toxicity in patients with dihydropyrimidine dehydrogenase (DPYD) deficiency

BACKGROUND

5-Fluorouracil (5-FU), an analog of uracil, is one of the most commonly used chemotherapeutic agents and like other agents has a narrow therapeutic index limited by toxicity. Compared to previous attempts, uridine triacetate (Vistogard) has shown to increase the potential efficacy of 5-FU by allowing administering a higher dose and decreasing the toxicity. Recently, Vistogard received orphan drug designation from the FDA as an antidote in the treatment of 5-FU poisoning and from the European Medicines Agency as a treatment for 5-FU overdose. However, no data have been published to date in humans who were rescued by this agent following severe toxicity associated with 5-FU due to dihydropyrimidine dehydrogenase (DPYD) deficiency, the enzyme which is responsible for the elimination of approximately 80 % of the administered dose of 5-FU.

PATIENTS AND METHODS

We identified two patients with advanced pancreatic cancer who were referred to us for testing of DPYD status following severe toxicity associated with 5-FU administered at a dose of 1400 mg/m(2) weekly bolus high-dose 5-FU followed by oral uridine triacetate as a part of a clinical trail. One patient developed grade 3 thrombocytopenia and grade 3 skin rash that resolved with discontinuation of 5-FU and supportive care, while second patient developed grade 4 thrombocytopenia, grade 3 coagulopathy and grade 3 neurological toxicity with a fatal outcome. DPYD status was evaluated as we have previously published.

RESULTS

The first patient was found to have an abnormally low DPYD activity of 0.087-nmol/min/mg protein by radioisotopic assay (reference normal range 0.182-0.688 nmol/min/mg protein). Because of pancytopenia, DPYD enzyme activity could not be assessed in patient 2; genotypic analysis of DPYD during autopsy revealed the presence of the heterozygous mutation, IVS14+1 G>A, DPYD*2A, now recognized as the most common cause of DPYD deficiency.

CONCLUSION

These two patients present the first two cases of DPYD deficiency that had either delay in severe toxicity or recovered from severe toxicity as they received oral Vistogard as a part of the conical trial. Toxicity was delayed in both patients by a mean of 3.5 weeks (range 3-4 weeks), indicating that Vistogard might be able to delay 5-FU toxicity despite higher doses than standard bolus dose of 5-FU used in gastrointestinal malignancies and the appearance of a potentially less toxic adverse effect of 5-FU at an unusual site (cutaneous) in one patient. The role of uridine triacetate with 5-FU in DPYD-deficient patients needs further investigation.

In vivo protective effect of Uridine, a pyrimidine nucleoside, on genotoxicity induced by Levodopa/Carbidopa in mice

Parkinson's disease (PD) is a common neurodegenerative disorder that affects millions of people all over the world. Motor symptoms of PD are most commonly controlled by L-3,4-dihydroxyphenylalanine (Levodopa, L-DOPA), a precursor of dopamine, plus a peripherally-acting aromatic-L-amino-acid decarboxylase (dopa decarboxylase) inhibitor, such as carbidopa. However, chronic treatment with a combination of Levodopa plus carbidopa has been demonstrated to cause a major complication, namely abnormal involuntary movements. On the other hand, the effect of this treatment on bone marrow cells is unknown. Therefore, in this study, we aimed to investigate possible genotoxic effects of Levodopa and Carbidopa using male Balb/C mice. Our results showed that Levodopa alone or in combination with carbidopa caused genotoxicity in in vivo micronucleus test (mouse bone marrow) and Comet assay (blood cells). Furthermore, we showed that simultaneous administration of uridine, a pyrimidine nucleoside, reversed the genotoxic effect of Levodopa and Carbidopa in both assays. Our data show for the first time that Levodopa plus carbidopa combination causes genotoxicity which is reversed by uridine treatment. These findings might enhance our understanding for the complications of a common Parkinson's treatment and confer benefit in terms of reducing a possible genotoxic effect of this treatment.

Photophysical properties of zinc phthalocyanine-uridine single walled carbon nanotube--conjugates

The photophysical properties of the conjugate of uridine and zinc mono carboxy phenoxy phthalocyanine (ZnMCPPc-uridine, 4) are reported in this work. The conjugate was also adsorbed onto single walled carbon nanotubes (ZnMCPPc-uridine-SWCNT, 5). The X-ray photoelectron spectroscopy of 4 showed three N 1s peaks while that of 5 showed four N 1s peak, a new peak at 399.4 eV of 5 was assigned to pyrrolidonic nitrogen, due to the interaction of the pyrrolic nitrogen of 4 with the oxygen moiety of SWCNT-COOH in 5. The triplet lifetime, triplet and singlet oxygen quantum yields of the zinc mono carboxy phenoxy phthalocyanine increased by over 40% in the presence of uridine. SWCNTs resulted in only a small quenching of the triplet state parameters of 4.

Evidence for the existence of pyrimidinergic transmission in rat brain

The uridine nucleotides uridine-5'-triphosphate (UTP) and uridine-5'-diphosphate (UDP) have previously been identified in media from cultured cells. However, no study to date has demonstrated their presence in brain extracellular fluid (ECF) obtained in vivo. Using a novel method, we now show that UTP and UDP, as well as uridine, are detectable in dialysates of striatal ECF obtained from freely-moving rats. Intraperitoneal (i.p.) administration of uridine or exposure of striatum to depolarizing concentrations of potassium chloride increases extracellular uridine, UTP and UDP, while tetrodotoxin (TTX) decreases their ECF levels. Uridine administration also enhances cholinergic neurotransmission which is accompanied by enhanced brain levels of diacylglycerol (DAG) and inositol trisphosphate (IP3) and blocked by suramin, but not by PPADS (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid) or MRS2578 suggesting a possible mediation of P2Y2 receptors activated by UTP. These observations suggest that uridine, UTP and UDP may function as pyrimidinergic neurotransmitters, and that enhancement of such neurotransmission underlies pharmacologic effects of exogenous uridine on the brain.

Synthesis and biological evaluation of 5'-glycyl derivatives of uridine as inhibitors of 1,4-β-galactosyltransferase

New 5'-glycyl derivatives of uridine containing fragments of varying lipophilicity were synthesized as analogues of natural peptidyl antibiotics. One of the studied compounds, 5'-O-(N-succinylglycyl)-2',3'-O-isopropylideneuridine (A4), showed moderate inhibition against 1,4-β-galactosyltransferase. However, additional studies showed that the observed inhibitory effect was due to binding to bovine serum albumin, which was used in assays as a stabilizer.

Uridine decreases morphine-induced behavioral sensitization by decreasing dorsal striatal dopamine release possibly via agonistic effects at GABAA receptors

Uridine, a potential endogenous neuromodulator, has been demonstrated to interact with the dopaminergic system and to regulate dopamine-related behaviors. The present study investigated the effects of uridine on morphine-induced hyperactivity and behavioral sensitization and on modulating dopaminergic neurotransmission in mice, which may help to understand how uridine and its metabolites act as modulators of the GABAA receptors. The results showed that either systemic (30 or 100mg/kg) or central (30, 100 or 300nM) uridine administration significantly attenuated the hyperactivity induced by acute morphine treatment in mice. Intracerebroventricular administration of uracil and β-alanine also inhibited morphine-induced hyperactivity. Uridine, a known modulator of the GABA receptors, increased the extracellular levels of GABA in the brain. In addition, the GABAA receptors antagonist bicuculline significantly attenuated the effects of uridine on morphine-induced hyperactivity, suggesting that the GABAA receptors potentially mediate the effects of uridine and its metabolites on morphine-related activity. It was also observed that morphine-induced locomotor sensitization was abolished after chronic uridine treatment. In vivo microdialysis demonstrated that uridine reversed morphine-induced dopamine release in the dorsal striatum of morphine-sensitized mice. In conclusion, these data suggest that the therapeutic effects of uridine and its metabolites on morphine-induced hyperactivity and established behavioral sensitization may be mediated in part by interfering with the dopaminergic system possibly via agonistic effects at GABAA receptors.

Pharmacokinetics of uridine following ocular, oral and intravenous administration in rabbits

The pyrimidine nucleoside uridine has recently been reported to have a protective effect on cultured human corneal epithelial cells, in an animal model of dry eye and in patients. In this study, we investigate the pharmacokinetic profile of uridine in rabbits, following topical ocular (8 mg/eye), oral (450 mg/kg) and intravenous (100 mg/kg) administration. Blood and urine samples were serially taken, and uridine was measured by high-performance liquid chromatography-tandem mass spectrometry. No symptoms were noted in the animals after uridine treatment. Uridine was not detected in either plasma or urine after topical ocular administration, indicating no systemic exposure to uridine with this treatment route. Following a single intravenous dose, the plasma concentration of uridine showed a bi-exponential decay, with a rapid decline over 10 min, followed by a slow decay with a terminal half-life of 0.36 ± 0.05 h. Clearance and volume of distribution were 1.8 ± 0.6 L/h/kg and 0.58 ± 0.32 L/kg, respectively. The area under the plasma concentration-time curves (AUC) was 59.7 ± 18.2 μg·hr/ml, and urinary excretion up to 12 hr was ~7.7% of the dose. Plasma uridine reached a peak of 25.8 ± 4.1 μg/ml at 2.3 ± 0.8 hr after oral administration. The AUC was 79.0 ± 13.9 μg·hr/ml, representing ~29.4% of absolute bioavailability. About 1% of the oral dose was excreted in the urine. These results should prove useful in the design of future clinical and nonclinical studies conducted with uridine.